Effects of cavity length on 20 μm stripe laser waveguiding

Measurements have been made on a number of lasers, cleaved to different lengths, but otherwise identical. The lasers used were simple planar oxide-insulated devices with stripe widths of about 18 nm and lengths from 225 to 600μm. The parameters measured were: threshold current, maximum power for zero-order-mode operation, and near-field widths (parallel to the junction). The variations of measurable parameters with length are shown to agree with first-order theory. A sophisticated numerical model has also been used to calculate the variables measured, using only material parameters and device dimensions. The values obtained are generally in good agreement with those measured, showing that, despite the complex behaviourof this weakly guided device, it is possible to model its behaviour with confidence.